In my previous U.S. Pat. No. 3,807,899, I described a device having a pair of spaced cross arms that rode in upper channels and which had coincident bores within each arm for aligning holes to be drilled. I have now invented a related but simplified device that also uses the concept of a cross arm riding in spaced channels for self-centering upon the edge of a board for the locus of a hole to be drilled.
Whereas my patented device has two cross arms, this device has only one cross arm. Just as the previous unit used a single tightening screw and self-locating pins, so too does this invention.
While my previous device worked well, the complexity of it and the high cost of manufacture kept it from being a big seller. In the interim, however, no other, better, device has reached the marketplace, though there have been developments to be found in the patent literature.